The diathesis/stress model of schizophrenia holds that the disorder develops through the interaction of a genetically transmitted predisposition and unspecified environmental events. Vulnerability is seen as a necessary, but not sufficient, cause of schizophrenia. Most theorists assume this condition will be reflected in directly observable behaviors which are relatively stable and enduring characteristics of vulnerable individuals. Specific cognitive difficulties may be among these variables. The present proposal describes two complementary, longitudinal studies which are designed to clarify the role that specific cognitive difficulties play in vulnerability to schizophrenia. More specifically, the studies will determine a) whether these problems are unique to schizophrenic patients, and b) whether they are stable characteristics in these individuals or, instead, transient epiphenomena associated with severe psychiatric disturbance. Several recent studies indicate that if cognitive variables do play a role in vulnerability to shcizophrenia, the best measures of that trait will be those that tap active, higher-level information processing abilities which are related to psycholinguistic performance. The proposed studies focus on several measures of controlled, short-term memory processes, including sentence comprehension, short-term recall, and referential speaking. The first study involves testing groups of schizophrenics, manics, unipolar depressives, and non-psychiatric patients upon admission to the hospital and again when they are discharged. The psychiatric patients will be retested six months after leaving the hospital. In the second study, similar groups of outpatients who have "recovered" from acute psychotic episodes will be tested at successive 6-month intervals. The outcome of these studies should provide important empirical information regarding the course of schizophrenic disorder and will be useful in the rational selection of potentially meaningful indices of vulnerability.